Means for silencing gaseous currents



March 30, 1937. J. BLANCHARD MEANS FOR SILENCING GASEOUS CURRENTS FiledNOV. 50, 1955 Patented Mar. 30, 1937 t UNITED STATES PATENT oFFicEJoseph motora, London, England, f1

o! one-half to Cecil asigna' Gordon Votes, london,

Application November 30,1935, sono: No. 52,434 In Great Britain December18, 1934 1, This invention relates to silencers for pulsating gaseouscurrents, such as the exhaust of ,internal combustion engines, theairintake of internal combustion engines or compressors, the

exhaust of pneumaticengines and the like.

It is an object ofthe invention to provide a silencer in which a. seriesof units or elements are employed each comprising' a passage into whichan inlet pipe projects at one end to form an injector eiective upon someor all of the 'contents of a space situated between the passage and anouter wall and communicating'also with the other end of thepassage.

'.It is a further object' of the invention to provide a silencerhaving'inner, intermediate and outer paths for gases and in which gasestraversing the intermediate path'are subject to the in- :lector effectof gases traversingl the inner path.

With these and other objects in view, the invention also consists in thenew or improved teatures, combinations and arrangements of partsembodied in the specific embodiments now to l'be described in detail,the novel aspects of the invention being pointed out in the claims whichfollow.

In the drawing.: .Y

Figure 1 is a longitudinal section through a silencer, u

Figure 2 is a similar section through part of a 30 modified form o fsilencer, l E

Figure 3 is a similar section through part of a further form ofsilencer, and

Figure 4 is a section on the line IV--IV of Figure 3. .A y

The cylindrical outer casing l of the silencer shown in Figure 1 hasinlet and outlet pipes 2 and 3 respectively and has mounted preferablyconcentrically within it a cylinder 4 of reticulated 'material supportedby perforated annuli 5. 40 A series of silencer units 6 is arrangedwithin the reticulated cylinder, which, as shown, does notv extend thewhole length ,of the silencer but is of such length'as to leave at theoutlet end a chamber l which is not occupied by silencer 45 units or bypart of the reticulated cylinder.

Each of the silencer units 6 comprises a pair of end plates 8 and 9 anda tube Il) of Venturi section. The end plates 8 and 9 comprise each anouter annular portion Il and a centralin- 50 wardly dished and aperturedportion llof greater length joined by an annular channel ofsubstantially segmental cross section. 'I'he end plates 8 and 9 oi' eachunit are secured at the opposite ends'oi' the Venturi tube 55 i0 of thatunit by means of radial tongues il weiden to the tube and the portionsl2 of the end plates respectively. The apertured. portion i l of theplate 8 forms aninlet passage projecting -into the passage formed by theVenturi tube and tube at the outlet end thereof, and thus places thisend also of the Venturi passage into com- 15 munication with .the spacesurrounding it.

The inlet passage of the iirst silencer unit, that on the `extreme leftinY'Figure .1, receives gases direct from the inlet pipe 2 of thesilencer and leads theminto the Venturi passage of that unit. Thesegases pass to the far end of the Venturi passage and it will be seenfrom the drawing that a straight-through path `is provided for them tothe outlet pipe 3 by way of the outlet passage of the rst unit andthrough the succeeding units. Some parts of the gases, however, nd theirway by the passage i6 to the space l5 the contents of which are subjectto the injector action of the gases entering through the inlet passage.This injector action has the effect of returning to the main flow, byWay of the opening I4, some of the gases withdrawn to the space l5 bythe passagel. v

The action vof the succeeding units is similar to that described above,and the gases which. pass through the outlet passage of the final, orextreme right hand, unit are led towards the outlet pipe 3 by a conicalirustum l1 of reticulated material situated within the chamber 1. Someof the gases` withdrawn from the main or central stream to the portionsi 5 of the space surrounding the Venturi passages of the various unitsare not'returned direct to the main flow by the injector action. whichcaused their withdrawal but pass by Way of the reticulations of thecylinder 4, to

the annular portion of the space vwhich is situated between the cylinderand the outer casing l. Some of the gases thus passing may be returnedtothe main ow by the injector action of succeeding units, but theremainder are drawn towards the outlet pipe 3 by the entraining actionof the high velocity gas stream leaving the small end of the cone.

It will be seen from the above description that some of the gasesforming the pulsating currents are withdrawn from the main stream andreturned to it at various points, thus tending to break up or reduce theoriginal pulsations. The lengths of the members I may vary in accord"- 5ance with the velocity of the gases entering at the inlet pipe at thenormal speed of the engine from which they come, or at the speed atwhich most efdcient silencing is required, and/or in accord- .ance withthe volume of gas to be evacuated, and the lengths of the members I0 insucceeding elements or units may be so chosen relatively to each otherthat a substantially continuous or nonpulsating ow of gases at the exitorifice is obtained. l5 If desired, provision may be made for causingwhirling motion of the gases passing through the silencer. Thus, forinstance, lsuitable deflector plates may be provided for causingwhirling motion of the gases within the chamber 'l,` either within orwithout the conical frustum I'l.

Whirling motion, if provided for in silencers according to the presentinvention, may be in a lsingle sense or it may be periodically reversed,and gases may be divided into two oppositely directed streams which meetwith an effect of collision or turbulence.

if it is desired to limit the space for expansion allowed to the gases,a fairing sleeve may be provided surrounding the Venturi tube, thusreducing the effective volume oi the space i5. ln Figure l a sleeve itof reticulated material is shown surrounding the Venturi tube l0 of 'theextreme right-hand unit, whereby a cushioning4 space i5 is formed whichmay serve to absorb pressure peaks in the gases traversing the space i5.

Although it is preferred to employ a, Venturi tube as part of theinjector system, the injector action may be obtained by the combinationci an inlet passage leading into a second passage of any suitable formso as to leave an opening between the inlet passage and the secondpassage whereby an injector eect is produced upon the space surroundingthe latter. rIfhe rformation of the inlet and outlet passages integrallywith the end plates of the units is not, of course, essential, but thecurved portions of the end plates illustrated serve as smooth guidingsurfaces for the gases leaving and entering the main iiow in theirpassage to and from the space I5.

In some cases the space surrounding the path of the main gas iiow may bedivided otherwise than by the Wall oi the reticulated cylinder or by afairing sleeve as described above, such other manner of division beingalternative or additional to those shown in Figure l. Thus, for example,a member may be provided surrounding the Venturi tube, or itsequivalent, but making contact therewith at the outlet end only, theother end being secured to the outer annular portion of the end plate 8of the unit. A space is thus formed surrounding the main flow of gasesand subject to the injector action of those gases since the space is incommunication with the opening I4. A vacuum is thus formed 'surroundingthe path of the main gas iiowand acts as a deadener of sound. Such aunit is shown in Figure 2, later to be referred to.

The silencer illustrated provides a straightthrough passage for thegases, which passage may be followed by the eye from the inlet 2 to theoutlet 3. Such a completely straight path may not always be provided,owing, for example, to

the slight off-setting of succeeding silencer units, or if severalseries of units are employed in parallel with common inlet and/or outletpipes, or

,unitasthecasemayba where the silencer includes whirling or collisonplates.

Figure2 illustrates a form of silencer comprising two diierent types ofunit in series, that shown on the left in the figure being of simple 5form from the manufacturing view point, but being generally suitable foruse only in cases in which overall 'diameter is not of great importance.

In this form, the silencer unit shown on the left comprises apair ofmembers 20 and 2| each l0 formed from a hemispherical stamping andhaving an internal apertured neck 22 or 23; the necks 22 and 23 form theinlet and outlet passage re-` spectively of the unit. A Venturi tube I0is secured in position by means of tongues I3, as l5 in the formpreviously illustrated, with its ends enclosing the ends of the necks.

It will be seen from the drawing that the interior of the unitcommunicates with the interior of the rest of the silencer only `by itsinlet and 20 outlet passages .so that all gases withdrawn through thepassage i6 to the space surrounding the Venturi tube are returned to themain flow by injector action by way of the opening I4.

The unit is shown mounted with its portions 20 25 and 2| in actualcontact with the outer casing I of the silencer. If it is preferred, theouter casing may be made of greater relative cross section so that theshell of the unit is spaced therefrom, with orvwithout the interventionvof packing ma- 30 terial.

In a still simpler form of this kind of unit, the heini-sphericalstampings may be apertured for the reception of inlet and outlet pipes.In such a form it might be found necessary to provide 35 guiding memberssurrounding these inlet and outlet pipes to provide smooth paths for thebypassed gases similar to those produced in the form illustrated.

The unit shown on the right in the ligure com- 40 prises a pair of endplates 8 and 9 similar to those lshown in Figure l and a Venturi tube||l the ends of which surround the inwardly projecting portions |2 ofthe end plates to which the tube is secured by tongues I3. Afrustoconical sleeve 3| 45 surrounds thetube I0 and is secured at oneend to the outlet end of that tube and at the other end to the outerannular portion of the end plate 8.

The space 32 formed between the tube IB and 50 the sleeve 3| is subjectto the injector eiect of the gases entering through the inlet of theunit with the result that a vacuum is set up in this space. Such avacuum situated between the path of the gases through the venturi andthe outer casing 55 of the silencer acts as a deadener of sound.

Holes 33 are formed in the outer portion of the end'plate 3 to prevent ahigh pressure zone being set up in the space 34 formed between thesleeve 3| and the outer wall I of the silencer. 60

If it is desirable to produce a silencer having a relatively smalldimension in one direction, the construction illustrated in Figures 3and 4 may be adopted. According to this construction, inlet and outletpipes 24 and 25 respectively project 65 into a. tube 26 of greaterdiameter mounted within thev casing I, the internal dimension oiwhich inone directionis but slightlyogreater than the external diameter of thetube 26. The annular spaces formed between the inner surface of the 70tube 26 and thebuter surfaces oi' the pipes 24 and 25 place the interiorof the tube 26 into communication with spaces 21 and 28 respectivelyformed at theIv opposite ends of the silencer or The spaces 21 and "-15ate guiding members for the by-passed gases may be provided and packingmaterial may be inserted,

if desired, in the spacesvbetween the tubes and casing appearing inFigure 5. Alternatively, the

whole of the interior of the casing not occupied by the pipes 24 and 25and tube 26 may be employed for the return of the gases, the pipes 29and 43l) being omitted, if the freedom of expansion l5 of the gases thuspermitted is not undesirable.

The above descriptions of specific forms of silencer are given merely asexamples of practical ways of carrying out the invention and variousmodifications may be made without departing from the invention.

I claimt- 1. A silencer for pulsating gaseous currents including aseries of elements each comprising an inlet passage, a second passagewhich has a substantially imperforate wall and into which said inletpassage projects with an appropriate opening to form an injector, anouter wall forming between itself and the wall of said second passage aspace to which the end of said second passage 30 remote from said inletpassage is open and upon some or all of the contents of which theinjector formed by said inlet and second passages is effective.

2. A silencer for pulsating gaseous currents inc luding a series ofelements each comprising an outer wall, an inlet passage, a secondpassage receiving the end of said inlet passage to form an injectoreffective, vupon the contents of a space formed between said outer walland the wall of said second passage, a passage connecting said secondpassage to aspace formed between its wall and said outer wall, and opento a space formed within said outer wall to provide a path for gasescommon to all elements and alternative to those provided by the secondpassages thereof.

3. A silencer for pulsating gaseous currents comprisingintercommunicating inner, intermediate and outer paths for gases, and aninlet passage projecting into said inner path to form an injectoreffective upon gases traversing said intermediate path.

4. A silencer for pulsating gaseous currents comprising a passage, anouter wall enclosing a space between itself and the wall oi saidpassage, a wall dividing said space into two portions open to oppositeends of said passage, and an inlet pipe projecting into said passagewith an appropriate opening to form an injector which tends to drawtowards the inlet end of the silencer the contents of thatA portion ofsaid space which is open to the inlet end of said passage.

5. A silencer for pulsating gaseous currents comprising a passage, anouter wall forming a space between itself and the wall of said passage,an inlet pipe projecting into one end of 'said passage to form aninjector tending to reinjector, an outer wall forming a space betweenVitself and the wall of said second passage, said space being open tosaid second passage at both ends thereof and subject to the action ofsaid injector which tends to return to said second passage gases whichhave passed therefrom, and a passage formed within said outer wall andforming, for gases which have passed from said second passage to saidspace, a path alternative to that provided by said second passage.

7. A silencer for pulsating gaseous currents comprising a passage, aninlet passage projecting into said first mentioned passage to form aninjector, an outer.wall forming between itself and the wall of saidfirst mentioned passage a space which is open to said first mentionedpassage at both ends thereof and of which the contents are subject tothe action of said injector, and a reticulated wall dividing said spaceinto two portions.

8. A silencer for pulsating gaseous currents comprising an outer casing,a tube of Venturi section arranged within said outer casing and an inletpipe for gases projecting into said Venturi tube to form an injectoreffective upon ythe contents of a space situated between the wall ofsaid Venturi tube and the wall of said outer casing.

9. A silencer for pulsating gaseous currents comprising a tube mountedwithin a casing, an inlet pipe projecting into said tube with anappropriate opening to form an injector effective upon the contents of aspace situated between said tube and said casing, and a sleevesurrounding said tube.

10. A silencer as claimed in claim 9 wherein said sleeve is ofreticulated material.

11. A unit for use in a silencer comprising a pair of end plates ofwhich each has an inwardly dished and `apertured portion, and a tube theends of which surround with clearance the ends of the inwardly dishedand apertured portions ofthe said end plates.

JOSEPH BLANCHARD.

